# Can you solve this? The concentration of the #Zn^(2+)# ions in blood serum is 1.2 ppm. Express this amount in terms of millimole/L and milliequivalent/L.

##### 1 Answer

The concentrations are

#### Explanation:

So, you know that the **ppm** concentration of zinc cations, **1.2 ppm**.

A **1 ppm** concentration means that you have *1 part* solute, in your case zinc cations, per **1 million** parts of solvent.

To get the ppm concentration, simply multiply the ratio that exists between the mass of the solute and the mass of the solvent by **1 million**, or

To make calculations easier, assume that you're dealing with a **1-L** sample of blood serum. The density of blood serum is know to be equal to

Use the definition of ppm concentration to determine what mass of zinc cations you have in solution

To express the concentration in milimoles per liter, you need to determine how many moles of

Expressed in milimoles, this is equal to

The concentration will thus be

To determine the concentration in miliequivalent per liter, you need to take into consideration the fact that normality only makes sense in the context of a chemical reaction.

An *equivalent* is simply a reactive unit - in your case, a reactive unit is a **monovalent cation**.

Since the zinc cation is actually a *divalent cation*, the number of equivalents will be equal to **2**.

This means that you have

Plug in your values to get

**SIDE NOTE** *I think that you can actually use the ppm concentration per liter of solution, which would make the mass of the zinc cations equal to*

*As you can see, the values are not that different*.